1. Field of the Invention
The present invention relates generally to an apparatus for testing the alignment of a transducer head, and more particularly to an alignment disk for use with disk drives to check the alignment thereof.
2. Description of the Prior Art
Proper alignment of the transducer head of a magnetic data storage device with the data tracks on a magnetic medium, whereby the transducer head fully and correctly reads data from the appropriate track, is essential to accurate data transfer. Computers are increasingly employed in a variety of applications in the home, business, scientific and educational environments. In particular, personal or microcomputers, having either integral or separate disk drives, are being employed to satisfy data processing needs. It can be appreciated that these environments are often very hostile to both the disk drive and to the magnetic storage media. Even slight changes in the alignment of the transducer head of a disk drive system can affect the ability of the disk drive to reliably read data recorded on the disk prior to the change in alignment, or recorded by another, properly aligned disk drive. Because of the interchangeability of flexible storage media, proper head alignment to a predetermined standard is necessary to ensure that data may reliably be read from various disks regardless of whether the disk was written by the same drive or by another drive.
While many methods of head alignment are possible, including complex servo systems which automatically adjust alignment, the most common practice with respect to flexible disk drives has been a manual adjustment performed by service technicians utilizing a specially recorded disk at an oscilloscope. This technique, known as the "cat's eye" alignment technique is described by Hersey, Jr. in U.S. Pat. No. 4,053,937. That technique, requires special equipment and a qualified technician.
Additional prior art attempts have been made to provide a means of checking alignment relative to magnetic recording devices. These however, are generally complex, expensive, and/or not amenable to flexible disk drives. U.S. Pat. No. 4,419,700, issued to Ragle et al. discloses a method and apparatus for recording on a magnetic disk in a spiral track configuration. U.S. Pat. No 4,415,939 issued to Ballard describes a servo encoding scheme and demodulation circuit for the control of the read/write head with respect to the magnetic disk. The apparatus of Ballard is not concerned with alignment monitoring per se, but with the actual apparatus for positioning of the head relative to the disk. U.S. Pat. No. 4,414,589 issued to Oliver et al. also discloses a servo track positioning system for accessing a plurality of concentric data tracks on a magnetic disk. U.S. Pat. No. 3,962,724 issued to Koizumi relates to a method and device for testing a transducer head of a disk drive utilizing a disk having a spiral track recorded thereon. However, the method and apparatus disclosed by Koizumi is not designed for disk drives used with flexible magnetic disks having data recorded in a plurality of concentric tracks. IBM Technical Disclosure Bulletin entitled "Helical Data Track Access Control," authored by F. Tsui and K. Tsui, Volume 15 No. 3, August 1972, discloses a servo system for accessing helical data tracks in a magnetic disk storage system.
In view of the prior art, there remains a need for a simple, effective and accurate method and apparatus for diagnosing transducer head misalignment, and related problems in flexible disk drives used with magnetic information storage systems.